Various personal authentication methods that use biometric information of an iris, a fingerprint, a face and the like have been proposed. In recent years, a personal authentication technique utilizing iris images has been started to be used for entrance/exit management in a restricted building, bank ATMs (Automated Teller Machines), PC login applications and the like.
Personal authentication utilizing iris images is proposed in Patent Reference 1, for example. In Patent Reference 1, an iris code is generated through the following steps:                1) Obtain an iris image;        2) Detect the pupil perimeter (pupil/iris border) and the iris perimeter (iris/sclera (white portion) border) from the obtained image to extract an iris region;        3) Transform the image of the iris region to a polar coordinate transformed images;        4) Apply multi-scale 2-d Gabor transformation to the polar coordinate transformed image; and        5) Binarize the real part and imaginary part of the Gabor transformed data to generate an iris code.        
Then, at the time of registration, an iris code for a registrant is generated through the above steps 1) to 5) and is registered in a registration database. On the other hand, at the time of authentication, an iris code for a person who is to be authenticated is generated through the above steps 1) to 5) and is compared with the iris code in the registration database to determine, based on a difference between the iris codes, whether or not he/she is a person who has been registered in the registration database.
(Patent Reference 1) Published Japanese translation of PCT international publication for patent application No. 8-504979